In general, a user purchases and uses software which is used in personal computer systems. A reasonable price is set for software as an outcome of the developer's time and effort.
Recently, however, a rapidly increasing number of users are installing and using software on their computer after purchasing only one software program, are copying software illegally after obtaining software through an illegal route, or are downloading software from the Internet. It demoralizes developer's will for development of software, obstructing the development of software.
In using software, although a purpose of using the software is to use it temporarily or for testing only, a user who tries to use the software legally has to pay for the entire software.
Recently, in order to solve aforementioned problem, web sites offering a rental service has become available for users who try to use specific software temporarily. However, users must always run software on-line to use the software even temporarily, and this causes inconvenience in using the software and is slow in case of increased access traffic. Moreover, there is a problem that the fee for using the software must be paid in advance and for a fixed period (e.g., one month, one year, etc.) regardless of the period of using the software.